Treating agricultural soils with propargyl phosphorothioates



signors to Monsanto Chemical Company, St. Louis, Mo., a corporation ofDelaware No Drawing. Application March 18, 1958 Serial No. 722,151

5 Claims. (Cl. 167-22) This invention relates to compositions useful inthe treatment of soil, particularly to compositions useful in destroyingparasitic worms present in the soil, and to a method of applying thesame. It further relates to the destruction of the parasitic worms knownas nematodes in any of the egg, larvae and adult stages of their lifecycles and particularly those harmful worms which attack crop plants andcause considerable damage thereto.

The problem 'of controlling harmful and unwanted parasites present inthe soil, such as nematodes, is one of considerable complexity, In orderto be an effective toxicant,; a: compound must be able to penetrate thenormally impervious outer covering of the worm as well as the enclosingmembranes of the larvae and eggs and to interfere with some vitalfunction of the organism. While the exact mechanism of destroying thesoil worm life is not fully understood, it is believed that theeifective toxicants destroy or reduce to a low level the efiectivenessof vital enzymes. A compound which is effec tive must be one that willremain in the soil in contact with the undesirable worm life for asuflicient period of time to effect the penetration of the worm and todestroy it by one means or another. To accomplish this result, it isnecessary that the toxicant resist the destructive action of soilbacteria, be capable of wetting or penetrating the parasite, possess asubstantial water dispersibility, be capable of ready mixture with thesoil and possess a sufiiciently low vapor pressure so that it does notevaporate before its destructive action is accomplished. Since theexacting requirements of any practical agent cannot be recognized bymethods other than by test, it is neces sary to observe theeflectiveness of chosen compounds against the life cycle of theparasite.

In accordance with the present invention it has been discovered thatpropargyl phosphorothioates are highly effectve for controlling soilinfesting organisms and particularly nematodes.

The compounds found to be especially eflective for the intended purposeconform to the structure ROX PXCHzCECH where R and R represent loweralkyl or lower alkoxy substituted lower alkyl groups and X is achalkogen of atomic Weight less than 40, at least one X being sulfur.The method whereby the compounds of this class may be obtained is setforth and claimed in application Serial No. 576,546, filed April 6,1956, by Baker et a1.

As specific embodiments of the invention, nematocidal activity wasdemonstrated by preparing a suspension of the nematode Panagrellusredivivus in water and observing through a microscope the motility ofthe organisms in the presence of 0.1% of the test material. The nematodein aqueous suspension will flex its body at a regular rate and as thenematocide takes effect, the rate of flexing decreases. In the followingtable, employing the com- .f nitd States Patent 0.

2,906,661 Patented S ept. 29, 1959 2 pounds of this invention, the lossof motility of the nematode is recorded. I I

In another experiment sterilized soil was infested with nematodes(Meloidogyne sp.) and diiferent portions treated with solutionscontaining dilferent concentrations of 0,0 dimethyl S(2propargyl)phosphorodithioate. After standing for a week, two-week oldtomato plants were transplanted in the test soil and also in untreated,heat-sterilized soil. The plants were allowed to grow for two months,then were harvested, the roots washed and examined for evidence ofinfection. Comparison to the untreated controls gave the phytotoxicityof the compound. For convenience in recording the index of infection andphytotoxicity in the table ,below,.the following rating keys were used:

Infestation Phytotoxicity 1-No infection.

2Infection, barely recognized. 3-Light infection.

4-Medium infection. 5-Heavy infection.

0-No evidence of phytotoxicity. l-S1ight toxicity.

2-Moderate toxicity. 3-Severely toxic.

4-No plant survival.

In actual usage any of the compounds within the preferred classdescribed may be added to the soil in solution, as an emulsion or waterdispersion but preferably is added in a solid formulation wherein theactive nematocide is distributed over some dry and permanentlyfree-flowing powder such as the clays, including bentonite andattapulgite or such materials as talc, diatomaceous earth, fullersearth, chalk, calcium carbonate and the like. These diluents possess theadded advantage of lower cost treatment since normally they comprisemore than 50% up to 98% of the complete formulation and thereby providea means of more even distribution of the active material over a widerarea and in the effective quantities required. These nematocidalcompositions will of course attack the soil phase of the life cycle ofnematode parasites which infest animals. Treating barnyards, chickenpens, stables and other infested areas destroys eggs and infectivelarvae of many parasites which infest animals. Moreover, thecompositions are effective for the control of nematodes in theirenvironment which includes bodies of animals. They are toxic to otherworms such as flukes and tapeworms.

In the use of propargyl phosphorothioates as nematocides or soilfumigants the active compound, diluted or undiluted, may be applied tothe soil at rates of 10 to 500 pounds per acre. The preferredapplication for treating soils of average nematode infestation will befrom 25 to 100 pounds per acre. The formulation may contain dispersantswhich aid uniform distribution.

ROX

where R and R are selected from the group consisting of lower alkyl andlower alkoxy substituted lower alkyl groups and X represents a chalkogenof atomic weight less than 40, at least one of which is sulfur.

2. The method of destroying parasitic worm life in nematode infestedagricultural soils which comprises contacting the said organism with atoxic concentration of a compound of the structure where R and Rrepresent alkyl groups containing less than 3 carbon atoms.

3. The method of destroying parasitic worm life in nematode infestedagricultural soils which comprises contacting the said organism with atoxic concentration of a compound of the structure R0\fi POCHICECH ROwhere R and R represent alkyl groups containing less than 3 carbonatoms.-

4. The method of destroying-parasitic worm life in nematode infestedagricultural soils which comprises contacting the said organism with atoxic concentration of a compound of the structure CHaO\fi PSCHIOECH 5.The method of destroying parasitic worm life in nematode infestedagricultural soils which comprises contacting the said organism with atoxic concentration of a compound of the structure CzH5O S POCHICECHReferences Cited in the file of this patent UNITED STATES PATENTS BirnumDec. 31, 195.7 Kosmin a. Dec; 31, 1957

1. THE METHOD OF DESTROYING PARASITIC WORM LIFE IN NEMATODE INFESTEDAGRICULTURAL SOILS WHICH COMPRISES CONTACTING THE SAID ORGANISM WITH ATOXIC CONCENTRATION OF A COMPOUND OF THE STRUCTURE.